The effects of postsecondary experiences on the development of young people's aspirations, attitudes, and self-conceptions during their first four years after high school were studied. Attention was directed to self-esteem; orientations toward work, family, and community; sex-role attitudes; educational expectations; career aspirations; satisfaction with career progress; and locus of control. The source of data was the National Longitudinal Study (NLS) of the High School Class of 1972, a large panel study of more than 22,000 high school seniors. To determine the effects of career and educational choices on the outcomes of education, comparisons were undertaken of groups that entered different postsecondray tracks following high school graduation, including some type of postsecondary education, entry into the civilian labor force, military service, full-time homemaking, and unemployment. An individual effects model was used to adjust observed outcomes over a four-year period for initial differences in ability, high school achievement, family background, and other factors. In addition, changes in outcome measures over time were analyzed, based on a different set of assumptions. Theoretical perspectives concerning the self-concept and its relationship to life choices made in young adulthood are briefly considered, and the NLS database and study methodology, including the development of the Career Aspiration Index, are examined. The main finding is that the initial differences between young people who enter various postsecondary tracks are generally much greater than relative changes that emerge thereafter. Postsecondary experience generally had less effect on attitudes and aspirations than the factors that led to their initial choices. A bibliography is appended. (SW)